Part 1
OBD (II)INTRODUCTION
General
This manual is intended for trained automotive workshop personnel who have successfully completed Porsche training seminars on the respective systems and who possess the necessary theoretical and practical knowledge to perform work on complex systems.
The basic prerequisite for all work on the DME is the acknowledgement and observance of safety regulations and warnings; these are contained in the chapter "Notes" on the following pages.
NOTE: The following diagnosis and troubleshooting procedures are oriented toward and described for left-hand drive vehicles. Plugs and jacks specified may have different pin assignments for right-hand drive vehicles, which could lead to both misinterpretation during troubleshooting and to unpredictable accidents. Therefore, work should not be performed on right-hand drive vehicles without the correct circuit diagram or diagnosis and troubleshooting descriptions for right-hand drive vehicles.
This OBDII manual DME 7.1.1 covers the following vehicles:
- Cayenne with V8 turbo engine, as of model year 2003
- Cayenne with V8 naturally-aspirated engine, as of model year 2003
- Cayenne with V6 naturally-aspirated engine, as of model year 2004
This manual describes the diagnosis and troubleshooting procedures for the engine control module DME 7.1.1. It is based on the OBD II versions (USA version, OBD = On-Board Diagnosis). This includes the EOBD (European OBD) and RoW (Rest of the World) versions that were adapted to the respective national laws or regulations regarding diagnosis.
The main differences between the OBD II and EOBD versions include the fuel tank leakage test required by law in the USA and the criteria for storing faults and activating the CHECK ENGINE light (abbreviated CE below), which is also referred to as the MIL (Malfunction Indicator Light).
The following functions are assured by the OBD II system:
- Detection of combustion misfiring
- Monitoring the Efficiency of the Catalytic Converter
- Monitoring the fuel tank ventilation system
- Monitoring the fuel tank system for leaks
- Monitoring secondary air injection.
- Monitoring the adaptation limits (e.g. of oxygen sensing, boost pressure control)
- Monitoring the oxygen sensors
- Monitoring the thermostat and water temperature sensor
- Monitoring positive crankcase ventilation (via lambda adaption).
- Monitoring the transmission (Tiptronic control module)
- Monitoring emission-relevant sensors and actuators associated with the DME (previous scope of OBD 1)
- Triggering the Check Engine light and storing faults in the memory
- Indication of monitoring readiness (Ready codes, see "Ready status" entitled "Definition of terms")
- Output of existing diagnostic trouble codes (DTCs)
- Storage of defined operating parameters in the event of a fault (including freeze frame)
- Functional checks of the OBD system (warm-up cycle, driving cycle)
- Communication with standardised control-module tester (scan tool) in the prescribed modes
- Standardised read-out of operating data such as rpm, temperature, etc.
Digital engine control module DME 7.1.1
Location of DME control module
DME 7.1.1 is a proven, highly reliable engine control module, which was specially adapted to suit Porsche requirements. It is located under a cover in the right-hand part of the plenum chamber (engine compartment) and is protected against penetrating moisture.
Unlike with the DME control modules Porsche used previously, the fault memory is retained even after the battery is disconnected. It is especially important to bear this fact in mind when installing control modules as a test and then returning them to storage or installing them somewhere else. In cases such as this, the fault memory must be erased again before removing the control module.
When the voltage supply is interrupted, the following control module values will be deleted:
- All adaption values
- Learned values of the throttle adjusting unit
- Ready statuses of the individual diagnosis routines (see following chapter)
- Freeze frames (ambient conditions) stored with the faults
Bear in mind that programming the DME (e.g. loading a new data record) will also delete the values mentioned above.
Note on adaption
The DME control module must perform a learning and adaptation routine for the throttle valve adjuster if:
- the power supply to the DME control module was interrupted,
- the DME control module connectors were unplugged,
- a new DME control module was installed,
- the throttle valve adjuster was replaced,
- the DME was programmed.
To initiate adaption:
1. Switch on the ignition without starting the engine
2. Perform a "throttle adaptation" under the "System adaptation" column using the 9588 Porsche System Tester II.
The following conditions must be met, otherwise adaptation is not possible:
- Do not press the accelerator (make sure there is no carpet pressing on the accelerator, for example)
- Stationary vehicle
- Battery positive voltage between 10 V and 16 V
- Engine temperature between 5 °C and 100 °C
- Intake air temperature > 10 °C
Standardised fault codes according to ISO 15031
Diagnostic trouble codes that can be issued by the control module are standardised according to ISO 15031. This ISO standard is based on SAE J 2012.
The fault code or DTC is always a 5-character alphanumeric value, e.g. "P0100".
The first character (letter) of the code identifies the system which has set the code. A total of four system types are covered:
- P for powertrain (this is the first character of all OBD II fault codes)
- C for chassis
- B for body
- U for future systems
The P codes are classified in 2 main categories according to ISO 15031:
- Uniformly standardised codes: P0XXX and P2XXX; these codes are identical for all manufacturers
- Manufacturer codes: P1XXX and P3XXX: only the first 3 characters are standardised here (example: P13XX for ignition-system diagnosis or misfire detection); the last two characters are freely selectable by the manufacturer.
Only the P codes are required for OBD II.
The standardised codes are subdivided as follows:
P0001 to P0299 Fuel and air metering
PO3xx Ignition system and misfire detection
PO4xx Additional emission control systems
PO5xx Speed and idle air control
PO6xx Computer and output signals
P0700 to P0999 Transmission
P2000 to P2299 Fuel and air metering
P23XX Ignition system and misfire detection
P24XX Additional emission control systems
P25XX Additional input signals
P26XX Computer and output signals
P27XX Transmission
P28XX Reserved
P29XX Fuel and air metering
Definition of terms
Warm-up cycle
The warm-up cycle is the time which the engine requires to reach operating temperature. To fulfil the 'warm-up cycle' condition, the engine temperature on start-up must not be higher than a specified value (currently 44 °C). The engine operating phase has to be long enough to produce a certain temperature increase (currently 21 °K but the temperature reached must be at least 54 °C). The warm-up cycle condition is needed to decrement (count down) the fault erasing counter in the event of faults that have been recognised as "healed" (see 'Fault healing').
Driving cycle
A driving cycle consists of starting the engine, possibly a test drive (with a share of idling, partial load, constant driving, and overrunning phase) and the time between stopping the engine and starting again. For the purpose of shedding/healing faults, the driving cycle must sometimes include performing the relevant diagnosis.
Ready status
The "Ready Status" menu item indicates whether the OBD system has performed the required fault checks since the last time the 'fault memory was erased' or 'reset'. If a check proves to be OK, the one- off check is sufficient for a Ready status; if the system is faulty, the Ready status is achieved after a second check.
This is important, for example, for Inspection and Maintenance; this is where it is possible to detect whether the fault memory of a faulty vehicle was erased before the examination, without the cause(s) of the fault having been remedied.
The ready status is displayed for the following sub-systems:
- Oxygen sensor heater
- Oxygen sensor
- Secondary-air system
- Fuel tank ventilation system
- Cat. conv. efficiency
Once the Ready status has been reached for a sub-system, this is stored until the next time the 'fault memory is erased'.
NOTE:
- In some countries (currently: USA, Canada), it is necessary to restore the Ready status following manipulation of the DME before the vehicle is supplied to the customer
- To do this, you must perform the short test available in the 9588 Porsche System Tester II or a test drive to achieve the relevant diagnostic conditions (these are listed for each system at the beginning of the test instructions for P codes in this manual)
- If you have any questions, please contact your nearest importer
Freeze frames (officially prescribed 'frozen fault boundary conditions')
Freeze Frame data is standardised and records the operating conditions in the (first) event of a fault. Freeze frames have different priorities. This can be significant when output to a scan tool since it may only be possible to display one freeze frame here although several faults are stored (misfire or fuel supply faults overwrite the freeze frames of other faults).
Freeze frames can be examined in the "extended fault memory" of the 9588 Porsche System Tester II.
The control module must be able to output the following freeze frame data to a standardised diagnostic device (scan tool):
- DTC that caused this freeze frame to be stored
- Engine load
- Engine speed
- Coolant temperature
- Oxygen sensor status (control or sensing)
- Mixture adaptation values
- Fuel pressure (when available, not for DME 7.1.1 at present)
- Intake manifold pressure (when available, only for turbo vehicles at present in the case of DME 7.1.1)
- Vehicle Speed
With DME 7.1.1, a freeze frame is stored whenever a fault occurs for the first time. This freeze frame contains all the actual values listed above.
Other ambient conditions
Each time a fault occurs, two other operating conditions (actual values at the time the fault occurred), as well as the operating time and even the total number of kilometers/miles, are stored in DME 7.1.1.
This includes one memory entry for the first occurrence of the fault (the entry is stored) and a further entry for the last occurrence of the same fault (the entry is updated each time the fault recurs). This data can provide troubleshooting clues for difficult diagnoses, and can only be examined in the "extended fault memory" of the 9588 Porsche System Tester II. The list of possible ambient conditions overlaps at present with the freeze frames in order to store important ambient conditions even after the first occurrence of the fault.
Fault shedding (confirmation of a suspected fault)
When a fault occurs for the first time during a diagnostic routine it is stored as a suspected fault. At the same time, a fault shedding counter is started that contains a certain value (e.g. 2). During additional diagnostic procedures, the shedding counter will be decremented by 1 if the fault is recognised in the same area window. When the shedding counter has reached the value 0, the fault is considered as shedded and is thus entered. If the fault class provides for this, the CE light is now activated as well.
Fault healing (CE light off)
When a fault occurs for the first time during a diagnostic routine, it is stored as a suspected fault. This suspicion is either confirmed (the fault occurs again) or refuted (the fault does not occur again, no display on a scan tool) in the subsequent driving cycle. If the fault activates the CE light, a fault healing counter that contains a certain value (e.g. 5) is started at the same time. During additional diagnostic routines, the fault healing counter will be decremented by 1 if the fault is not recognised in the same area window. When the fault healing counter has reached the value 0, the fault is considered to be healed. If the fault has triggered the Check Engine light, then the latter is switched off as long as this is not prevented by any other faults. The fault remains in the fault memory for the time being; it is not deleted again until a certain number of warm-up cycles (defined in the fault erasing counter) are completed successfully (as workshop help, e.g. if the tank cap is not screwed on tightly for a short time).